A month-long moratorium on transuranic waste shipments using filler material commonly known as dunnage ended in early June, a spokesperson for DOE’s Waste Isolation Pilot Plant said this week.

The Waste Isolation Pilot Plant in New Mexico notified DOE that transuranic waste generators were estimating the weight of their payloads, including the dunnage, instead of weighing them out as required by Nuclear Regulatory Commission Rules, the Waste Isolation Pilot Plant (WIPP) spokesperson said. 

The practice of estimating payload weights, widespread across the weapons complex, had gone on for about two years, according to an NRC spokesman, David McIntyre. WIPP Prime Nuclear Waste Partnership found generator sites were calculating overpack weights by picking a nominal weight value archived in the DOE’s Waste Data System software and adding 5% to that value. 

While the practice of estimating shipment weight might result in shipments that are lighter than their listed weight, generators wound up in trouble because they did not do things strictly by the book, according to the Defense Nuclear Facilities Safety Board (DNFSB). The board highlighted the practice in a report dated June 4.

The Nuclear Regulatory Commission regulates nuclear-waste shipping containers, including TRUPACT-II and HalfPACT rigs used to move waste to WIPP. The Commission’s certificates of compliance for these containers require shippers to weigh out the containers, the waste and the dunnage, a spokesperson for the Commission, McIntyre,  wrote Tuesday in an email.

“There is no safety issue, and no overweight packages were shipped,” McIntyre wrote. “The issue is that they didn’t calculate the weights the way they were required to in the Certificates of Compliance for these two packages,” McIntyre wrote. 

“Any deviation from the NRC certification criteria/parameters is taken seriously,” the DOE spokesperson said. “Controls were put into place to ensure that the actual dunnage container weight is properly recorded.”

The dunnage in transuranic waste shipments performs much the same function as packing material in consumer shipments, by keeping contents from shifting during transport. The dunnage included in shipments headed to WIPP are approved, 55-gallon drums or standard waste boxes typically holding wood, the DOE spokesperson said. 

WIPP, which tipped off the Nuclear Regulatory Commission, performed “an extent of condition review,” prior to holding up dunnage shipments, according to a DNFSB staff report dated June 4 and recently posted online.

The Idaho National Laboratory, one of the shippers out of compliance, had to temporarily ship full payloads without dunnage, according to a second DNFSB staff report also dated June 4. Contractor Fluor Idaho has enough containers with full payloads to ship for four-to-six more weeks, the board report said.